Exploring the Impression of Minor Bacterial Pathogens on Human Well being: An In-depth Evaluation of Lesser-Identified Microbial Threats

Exploring the Impression of Minor Bacterial Pathogens on Human Well being: An In-depth Evaluation of Lesser-Identified Microbial Threats

BACTERIA OF MINOR MEDICAL

IMPORTANCE

The bacterial pathogens of lesser medical significance are

briefly described on this chapter. Consultants could differ on their

alternative of which organisms to place on this class. Neverthe-

much less, separating the minor from the key pathogens ought to

enable the reader to deal with the extra necessary pathogens

whereas offering at the very least some details about the much less

necessary ones.

These organisms are introduced in alphabetical order.

Desk 27–1 lists the organisms in line with their look

on Gram stain.

Further info relating to the scientific facets of

infections attributable to the organisms on this chapter is offered

in Half IX entitled Infectious Illnesses starting on web page 589.

Abiotrophia

Abiotrophia species have been previously referred to as nutritionally defi-

cient streptococci. They’re members of the conventional flora of the

mouth and might trigger subacute bacterial endocarditis.

Achromobacter

Achromobacter species are gram-negative coccobacillary rods

discovered mainly in water provides. They’re opportunistic patho-

gens and are concerned in sepsis, pneumonia, and urinary tract

infections.

Actinobacillus (Aggregatibacter)

Actinobacillus species are gram-negative coccobacillary rods.

Actinobacillus actinomycetemcomitans is discovered as a part of the

regular flora within the higher respiratory tract. It’s a uncommon opportu-

nistic pathogen, inflicting endocarditis on broken coronary heart valves

and sepsis. Actinobacillus actinomycetemcomitans has been

renamed Aggregatibacter actinomycetemcomitans, however the for-

mer genus title Actinobacillus is usually used.

Aeromonas

Aeromonas species are gram-negative rods present in water,

soil, meals, and animal and human feces. Aeromonas hydrophila

causes wound infections, diarrhea, and sepsis, particularly in

immunocompromised sufferers.

Alcaligenes

Alcaligenes species are gram-negative coccobacillary rods discovered

in soil and water and are related to water-containing mate-

rials similar to respirators in hospitals. Alcaligenes faecalis is an

opportunistic pathogen, inflicting sepsis and pneumonia.

Arachnia

Arachnia species are anaerobic gram-positive rods that type

lengthy, branching filaments much like these of Actinomyces.

They’re discovered primarily within the mouth (related to dental

plaque) and within the tonsillar crypts. Arachnia propionica, the

main species, causes abscesses much like these of Actinomyces

israelii, together with the presence of “sulfur granules” within the lesions.

Arcanobacterium

Arcanobacterium haemolyticum is a club-shaped, gram-positive

rod that intently resembles corynebacteria. It’s a uncommon reason for

pharyngitis and continual pores and skin ulcers. The pharyngitis may be

accompanied by a rash resembling the rash of scarlet fever.

Arizona

Arizona species are gram-negative rods within the household Entero-

bacteriaceae; they ferment lactose slowly. Arizona hinshawii is

discovered within the feces of chickens and different home animals and

causes illnesses much like these attributable to Salmonella, similar to

enterocolitis and enteric fevers. The organism is often trans-

mitted by contaminated meals (e.g., dried eggs).

Bartonella quintana & Bartonella

bacilliformis

Bartonella quintana is the reason for trench fever and in addition is

implicated as the reason for some instances of bacillary angiomatosis.

Trench fever is transmitted by physique lice, and people are the

reservoir for the organism. Bartonella bacilliformis causes two

uncommon illnesses: Oroya fever and verruga peruana, each of which

are levels of Carrión’s illness. The illness happens solely in cer-

tain areas of the Andes Mountains, and an animal reservoir is

suspected.

Bifidobacterium

Bifidobacterium eriksonii is a gram-positive, filamentous, anaer-

obic rod discovered as a part of the conventional flora within the mouth and

gastrointestinal tract. It happens in combined anaerobic infections.

Bradyrhizobium

Bradyrhizobium enterica is a gram-negative rod that’s thought

to be the reason for twine colitis. Wire colitis manifests as non-

bloody diarrhea in sufferers who’ve obtained an allogeneic

hematopoietic stem-cell transplant of umbilical twine cells. It was

recognized through the use of DNA sequencing and polymerase chain reac-

tion (PCR) assays on contaminated tissue from biopsies of the colon.

Bradyrhizobium species are widespread soil micro organism that repair

nitrogen in leguminous crops. Bradyrhizobium enterica is the

first member of the genus to be recognized as a human opportu-

nistic pathogen.

Branhamella

Branhamella catarrhalis has been renamed Moraxella catarrhalis

(see Moraxella, later).

Burkholderia pseudomallei

Burkholderia pseudomallei (previously referred to as Pseudomonas

pseudomallei) is a gram-negative rod that causes melioidosis,

a uncommon illness discovered primarily in Southeast Asia. The organ-

ism is present in soil and is transmitted most frequently when soil

contaminates pores and skin abrasions. This illness has been seen within the

United States, as a result of infections acquired by members of the

armed forces in the course of the Vietnam Struggle have reactivated many

years later. The acute illness is characterised by excessive fever and

bloody, purulent sputum. Untreated instances can proceed to sepsis

and demise. Within the continual type, the illness can seem as pneu-

monia or lung abscess or could resemble tuberculosis. Analysis

is made by culturing the organism from blood or sputum. The

therapy of alternative is ceftazidime, which is run for

a number of weeks.

Calymmatobacterium

Calymmatobacterium granulomatis is a gram-negative rod that

causes granuloma inguinale (also called donovanosis), a

sexually transmitted illness characterised by genital ulceration

and gentle tissue and bone destruction. It’s uncommon within the United

States however endemic in lots of creating nations. The diagno-

sis is made by visualizing the stained organisms (Donovan

our bodies) inside giant macrophages from the lesion. Both doxy-

cycline or azithromycin is an efficient therapy for this illness.

Calymmatobacterium granulomatis is also called Klebsiella

granulomatis.

Capnocytophaga

Capnocytophaga gingivalis is a gram-negative fusiform rod that’s

related to periodontal illness, nevertheless it may also be an oppor-

tunistic pathogen, inflicting sepsis and mucositis in immunocom-

promised sufferers. Capnocytophaga canimorsus is a member of

the oral flora of canines and causes infections following canine bites.

It might probably additionally trigger sepsis in immunocompromised sufferers, espe-

cially these with no spleen and people who abuse alcohol.

Cardiobacterium

Cardiobacterium hominis is a gram-negative pleomorphic rod.

It’s a member of the conventional flora of the human colon, nevertheless it

may be an opportunistic pathogen, inflicting primarily endocarditis.

Chromobacterium

Chromobacterium violaceum is a gram-negative rod that pro-

duces a violet pigment. It’s present in soil and water and might

trigger wound infections, particularly in subtropical components of the

world.

Chryseobacterium

Chryseobacterium species are gram-negative rods present in

soil and water. Chryseobacterium meningosepticum, the key

pathogen on this genus, is an opportunistic pathogen, caus-

ing meningitis and sepsis, particularly in untimely infants. In

adults, it causes outbreaks of nosocomial pneumonia, particularly

in intubated sufferers. It’s proof against most antibiotics however is

noteworthy as the one gram-negative bacterium that’s suscep-

tible to vancomycin. The genus Chryseobacterium was previously

referred to as Flavobacterium.

Citrobacter

Citrobacter species are gram-negative rods (members of the

Enterobacteriaceae) associated to Salmonella and Arizona. They

happen within the atmosphere and within the human colon and might trigger

sepsis in immunocompromised sufferers.

Corynebacterium jeikeium

Corynebacterium jeikeium is a small gram-positive rod primar-

ily discovered on the pores and skin of hospitalized sufferers. It causes sepsis

in immunocompromised sufferers, most frequently those that are

neutropenic. Infections are sometimes related to indwelling

catheters and prosthetic coronary heart valves. The drug of alternative is van-

comycin. Hospital-acquired strains are proof against many different

antibiotics.

Corynebacterium minutissimum

Corynebacterium minutissimum is a small gram-positive rod

that causes erythrasma. Erythrasma is characterised by pruritic,

scaly, brownish macules on the pores and skin of the genital area. The

prognosis is often made by visualizing a coral-red fluorescence

with a Wooden’s lamp quite than by culturing the organism. The

drug of alternative is oral erythromycin.

Edwardsiella

Edwardsiella species are gram-negative rods (members of the

Enterobacteriaceae) resembling Salmonella. They will trigger

enterocolitis, sepsis, and wound infections.

Eikenella

Eikenella corrodens is a gram-negative rod that may be a member of

the conventional flora within the human mouth. It causes pores and skin and bone

infections related to human bites and “clenched fist” inju-

ries. It additionally causes sepsis and gentle tissue infections of the top

and neck, particularly in immunocompromised sufferers and in

drug abusers who lick needles previous to injection. Eikenella

corrodens can also be referred to as Bacteroides ureolyticus.

Erwinia

Erwinia species are gram-negative rods (members of the Entero-

bacteriaceae) present in soil and water and are hardly ever concerned in

human illness.

Erysipelothrix

Erysipelothrix rhusiopathiae is a gram-positive rod that causes

erysipeloid, a pores and skin an infection that resembles erysipelas (precipitated

by streptococci). Erysipeloid often happens on the fingers of

individuals who deal with meat and fish.

Eubacterium

Eubacterium species are gram-positive, anaerobic, non–spore-

forming rods which might be current in giant numbers as a part of the nor-

mal flora of the human colon. They hardly ever trigger human illness.

HACEK Group

It is a group of small gram-negative rods which have in widespread

the next: sluggish development in tradition, the requirement for top

CO2 ranges to develop in tradition, and the flexibility to trigger endocardi-

tis. They’re members of the human oropharyngeal flora and might

enter the bloodstream from that web site. The title “HACEK” is an

acronym of the primary letters of the genera of the next micro organism:

Haemophilus aphrophilus and Haemophilus paraphrophilus, Acti-

nobacillus (Aggregatibacter) actinomycetemcomitans, Cardiobacte-

rium hominis, Eikenella corrodens, and Kingella kingae.

Haemophilus aegyptius

Haemophilus aegyptius (Koch-Weeks bacillus) is a small gram-

detrimental rod that is a vital reason for conjunctivitis in chil-

dren. Sure strains of H. aegyptius trigger Brazilian purpuric

fever, a life-threatening childhood an infection characterised by

purpura and shock. This organism is also called Haemophilus

influenzae biogroup aegyptius.

Haemophilus ducreyi

This small gram-negative rod causes the sexually transmitted

illness chancroid (gentle chancre), which is widespread in tropi-

cal nations however unusual in america. The illness

begins with penile lesions, that are painful; nonindurated

(gentle) ulcers; and native lymphadenitis (bubo). The prognosis

is made by isolating H. ducreyi from the ulcer or from pus

aspirated from a lymph node. The organism requires heated

(chocolate) blood agar supplemented with X issue (heme)

however, not like H. influenzae, doesn’t require V issue (NAD).

Chancroid may be handled with erythromycin, azithromycin,

or ceftriaxone. As a result of many strains of H. ducreyi produce a

plasmid-encoded penicillinase, penicillins can’t be used.

Hafnia

Hafnia species are gram-negative rods (members of the Entero-

bacteriaceae) present in soil and water and are uncommon opportunistic

pathogens.

Kingella

Kingella kingae is a gram-negative rod within the regular flora of the

human oropharynx. It’s a uncommon reason for opportunistic an infection

and endocarditis.

Lactobacillus

Lactobacilli are gram-positive non–spore-forming rods discovered

as members of the conventional flora within the mouth, colon, and feminine

genital tract. Within the mouth, they could play a task within the produc-

tion of dental caries. Within the vagina, they’re the primary supply of

lactic acid, which retains the pH low. Lactobacilli are uncommon causes

of opportunistic an infection.

Micrococcus

Micrococci are gram-positive cocci which might be a part of the conventional

flora of the pores and skin. They’re uncommon human pathogens.

Mobiluncus

Mobiluncus species are anaerobic gram-positive, curved rods

that usually stain gram-variable. They’re related to bacterial

vaginosis in girls. Gardnerella (see above), a facultative rod,

is usually discovered on this illness as properly.

Moraxella

Moraxella species are gram-negative coccobacillary rods that

resemble the diplococcal look of the Neisseriae. Moraxella

catarrhalis is the key pathogen on this genus. It causes otitis

media and sinusitis, primarily in kids, in addition to bronchitis

and pneumonia in older folks with continual obstructive pulmo-

nary illness. It’s discovered solely in people and is transmitted by

respiratory aerosol. Trimethoprim-sulfamethoxazole or amoxicil-

lin-clavulanate can be utilized to deal with these infections. Most scientific

isolates produce β-lactamase. Moraxella nonliquefaciens is certainly one of

the 2 widespread causes of blepharitis (an infection of the eyelid);

Staphylococcus aureus is the opposite. The same old therapy is native

software of antibiotic ointment, similar to erythromycin.

Peptococcus

Peptococci are anaerobic gram-positive cocci, resembling staph-

ylococci, discovered as members of the conventional flora of the mouth

and colon. They’re additionally remoted from abscesses of assorted

organs, often from combined anaerobic infections.

Peptostreptococcus

Peptostreptococci are anaerobic gram-positive cocci discovered as

members of the conventional flora of the mouth and colon. They

are additionally remoted from abscesses of assorted organs, often from

combined anaerobic infections.

Plesiomonas

Plesiomonas shigelloides is a gram-negative rod related to

water sources. It causes self-limited gastroenteritis, primarily in

tropical areas, and might trigger invasive illness in immunocom-

promised people.

Porphyromonas

Porphyromonas gingivalis and Porphyromonas endodontalis are

anaerobic gram-negative rods discovered within the mouth. They trigger

periodontal infections, similar to gingivitis and dental abscesses.

Propionibacterium

Propionibacteria are pleomorphic, anaerobic, gram-positive

rods discovered on the pores and skin and within the gastrointestinal tract. Propi-

onibacterium acnes is a part of the conventional flora of the pores and skin and

may cause catheter and shunt infections. It’s concerned in combined

infections related to cat and canine bites and in head and

neck abscesses.

Propionibacterium acnes can also be concerned within the pathogenesis

of pimples, a situation that impacts greater than 85% of youngsters.

The pathogenesis of pimples entails impaction of the sebaceous

gland adopted by irritation attributable to the presence of P. acnes.

The pustules of pimples are composed of sebum, inflammatory

cells similar to neutrophils and lymphocytes, and the organism.

Antibiotics, similar to erythromycin, administered both topi-

cally or orally, are efficient, particularly when coupled with different

brokers similar to benzoyl peroxide or retinoids.

Rhodococcus

Rhodococcus equi is a gram-positive bacterium whose form

varies from a coccus to a club-shaped rod. It’s a uncommon reason for

pneumonia and cavitary lung illness in sufferers whose cell-

mediated immunity is compromised. The prognosis is made

by isolating the organism on laboratory agar and observing

salmon-pink colonies that don’t ferment most carbohydrates.

It could seem acid-fast and, if that’s the case, may be confused with

Mycobacterium tuberculosis. The therapy of alternative is a com-

bination of rifampin and erythromycin. (Rhodococcus equi used

to be referred to as Corynebacterium equi.)

Sarcina

Sarcina species are anaerobic gram-positive cocci grouped in

clusters of 4 or eight. They’re minor members of the conventional

flora of the colon and are hardly ever pathogens.

Spirillum

Spirillum minor is a gram-negative, spiral-shaped rod that

causes rat-bite fever (“sodoku”). The illness is characterised by

a reddish-brown rash spreading from the chunk, accompanied by

fever and native lymphadenopathy. The prognosis is made by a

mixture of microscopy and animal inoculation.

Streptobacillus

Streptobacillus moniliformis is a gram-negative rod that

causes one other sort of rat-bite fever (see Spirillum, previous

paragraph).

Streptococcus suis

In August 2005, it was reported that Streptococcus suis precipitated

the demise of 37 farmers in China. The sickness is characterised by

the sudden onset of hemorrhagic shock. This species is thought

to trigger illness in pigs however solely hardly ever in folks previous to this

outbreak. Unfold of the micro organism from the index case to others

has not occurred.

Tropheryma

Tropheryma whipplei is the reason for Whipple’s illness, a uncommon dis-

ease characterised by extended weight reduction, diarrhea, and polyar-

thritis. With out antibiotic therapy, it’s finally deadly. Infiltrates

of “foamy” macrophages in affected tissue, particularly within the small

gut, are generally seen. The reservoir of the organism, its

mode of transmission, and pathogenesis are unknown.

The character of this organism was unknown for a few years.

In 1992, it was recognized as an actinomycete when ribosomal

RNA taken from bacilli seen in duodenal lesions was com-

pared with ribosomal RNA of different micro organism. Tropheryma is

an intracellular organism that has been grown in human cell

tradition, however that process is just not used to diagnose the illness.

Laboratory prognosis is often made by periodic acid-Schiff

(PAS) staining of biopsy specimens of the small bowel wherein

inclusions are seen within the macrophages. PAS staining, nevertheless,

is nonspecific, and PCR assays, that are extra particular, are

used to substantiate the prognosis. First-line therapy sometimes

entails 2 weeks of ceftriaxone, adopted by at the very least 1 yr of

trimethoprim-sulfamethoxazole.

Veillonella

Veillonella parvula is an anaerobic gram-negative diplococcus

that’s a part of the conventional flora of the mouth, colon, and vagina.

It’s a uncommon opportunistic pathogen that causes abscesses of the

sinuses, tonsils, and mind, often in combined anaerobic infections.

Wolbachia

Wolbachia species are Rickettsia-like micro organism discovered intra-

cellularly inside filarial nematodes similar to Wuchereria and

Onchocerca (see Chapter 56). Wolbachia launch endotoxin-like

molecules which might be thought to play a task within the pathogenesis of

Wuchereria and Onchocerca infections. Remedy of sufferers

with Wuchereria and Onchocerca infections with doxycycline

to kill Wolbachia ends in a big lower within the quantity

of filarial worms within the affected person. Wolbachia themselves aren’t

identified to trigger human illness however do infect many species of

bugs worldwide. Alongside these traces, it’s attention-grabbing that the

neurotoxin of black widow spiders is encoded by WO virus, a

bacteriophage that infects Wolbachia micro organism.

Yersinia enterocolitica & Yersinia

pseudotuberculosis

Yersinia enterocolitica and Yersinia pseudotuberculosis are

gram-negative, oval rods which might be bigger than Yersinia pestis.

The virulence elements produced by Y. pestis aren’t made by

these species. These organisms are transmitted to people by

contamination of meals with the excreta of home animals

similar to canines, cats, and cattle. Yersinia infections are comparatively

rare in america, however the variety of documented

instances has elevated in the course of the previous few years, maybe because of this

of improved laboratory procedures.

Yersinia enterocolitica causes enterocolitis that’s clinically

indistinguishable from that attributable to Salmonella or Shigella.

Each Y. enterocolitica and Y. pseudotuberculosis may cause mes-

enteric adenitis that clinically resembles acute appendicitis.

Mesenteric adenitis is the primary discovering in appendectomies in

which a traditional appendix is discovered. Not often, these organisms are

concerned in bacteremia or abscesses of the liver or spleen, primarily

in individuals with underlying illness.

Yersinia an infection is related to two autoimmune dis-

eases: reactive arthritis and Reiter’s syndrome. Different enteric

pathogens similar to Salmonella, Shigella, and Campylobacter additionally

set off these illnesses. Reactive arthritis and Reiter’s syndrome

are described additional in Chapter 66.

Yersinia enterocolitica is often remoted from stool speci-

mens and varieties a lactose-negative colony on MacConkey’s

agar. It grows higher at 25°C than at 37°C; most biochemical

take a look at outcomes are optimistic at 25°C and detrimental at 37°C. Incuba-

tion of a stool pattern at 4°C for 1 week, a way referred to as chilly

enrichment, will increase the frequency of restoration of the organism.

Yersinia enterocolitica may be distinguished from Y. pseudotuber-

culosis by biochemical reactions.

The laboratory is often not concerned within the prognosis of

Y. pseudotuberculosis; cultures are hardly ever carried out in instances of

mesenteric adenitis, and the organism isn’t recovered from

stool specimens. Serologic assessments aren’t obtainable in most hospi-

tal scientific laboratories.

Enterocolitis and mesenteric adenitis attributable to the organ-

isms don’t require therapy. In instances of bacteremia or

abscess, both trimethoprim-sulfamethoxazole or ciprofloxacin

is often efficient. There aren’t any preventive measures besides to

guard towards contamination of meals by the excreta of home

animals.

SELF-ASSESSMENT QUESTIONS

1. Concerning Fusobacterium nucleatum, which one of many following

is most correct?

(A) Its pure habitat is the soil.

(B) It’s an anaerobic gram-negative rod with pointed ends.

(C) The drug of alternative for infections attributable to F. nucleatum is

azithromycin.

(D) Laboratory prognosis is predicated on detecting the flexibility of the

exotoxin to kill cells in tissue tradition.

2. Concerning Haemophilus ducreyi, which one of many following is

most correct?

(A) It requires each X and V elements to develop on MacConkey’s agar.

(B) Gram stain of exudate from the lesion exhibits giant gram-

optimistic rods.

(C) Penicillin G is the drug of option to deal with infections attributable to

H. ducreyi.

(D) It causes chancroid, which is characterised by a painful ulcer

on the genitals.

3. Concerning Yersinia enterocolitica, which one of many following is

most correct?

(A) It causes mesenteric adenitis, which might mimic appendicitis.

(B) It’s a gram-negative diplococcus discovered primarily inside

neutrophils.

(C) It’s the commonest reason for enterocolitis in america.

(D) Its pure habitat is the human oropharynx, and there’s no

animal reservoir.

4. Concerning Ehrlichia chaffeensis, which one of many following is

most correct?

(A) It’s transmitted primarily by mosquito chunk.

(B) It varieties β-hemolytic colonies on blood agar.

(C) Its commonest scientific presentation is acute meningitis.

(D) It’s endemic on the islands off the coast of Massachusetts (e.g.,

Nantucket).

(E) It varieties an inclusion physique referred to as a morula within the cytoplasm of

contaminated cell.

ANSWERS

(1) (B)

(2) (D)

(3) (A)

(4) (E)

SUMMARIES OF ORGANISMS

Temporary summaries of the organisms described on this chapter

start on web page 653. Please seek the advice of these summaries for a fast

assessment of the important materials.

PRACTICE QUESTIONS: USMLE &

COURSE EXAMINATIONS

Questions on the matters mentioned on this chapter may be discovered

within the Scientific Bacteriology part of Half XIII: USMLE

(Nationwide Board) Observe Questions beginning on web page 715. Additionally

see Half XIV: USMLE (Nationwide Board) Observe Examination